a) Field of the Invention
The present invention relates to a light source bulb in automotive headlamps, such as two-lamp type halogen headlamps, in which a prescribed low beam distribution pattern and high beam distribution pattern each can be obtained by entire-surface reflection light distribution control of the reflecting surface of a reflector, the light source bulb being capable of use both as a light source bulb in an automotive headlamp for right traffic and a light source bulb in an automotive headlamp for left traffic in one, without causing a problem of virtual image glare.
Incidentally, as employed in the present specification document and the accompanying drawings, the symbol xe2x80x9cAxe2x80x9d represents the front as seen from the driver-side along the traveling direction of an automobile. As seen in the same manner, the symbol xe2x80x9cBxe2x80x9d represents the back, the symbol xe2x80x9cLxe2x80x9d the left, the symbol xe2x80x9cRxe2x80x9d the right, the symbol xe2x80x9cUxe2x80x9d the upper, and the symbol xe2x80x9cDxe2x80x9d the lower. In addition, the symbols xe2x80x9cHL-HRxe2x80x9d represent a horizontal line seen in front from the driver-side (i.e., driver""s view), and the symbols xe2x80x9cHR-HLxe2x80x9d represent a horizontal line seen as the automobile- or the headlamp-side is viewed from the front (so-called front view or plane view). The symbols xe2x80x9cVU-VDxe2x80x9d represent a vertical line. Further, as employed both in the appended claims and in the present specification document, the terms xe2x80x9cfront,xe2x80x9d xe2x80x9cback,xe2x80x9d xe2x80x9cleft,xe2x80x9d xe2x80x9cright,xe2x80x9d xe2x80x9cupper,xe2x80x9d and xe2x80x9clowerxe2x80x9d each has the same meaning.
b) Description of the Prior Art
Automotive headlamps in which a prescribed low beam distribution pattern and high beam distribution pattern each can be obtained by entire-surface reflection light distribution control of the reflecting surface of its reflector include, for example, those described in Japanese Patent Laid-Open Publication No. Hei 8-329703.
Hereinafter, the outline of such an automotive headlamp will be described with reference to FIGS. 1 through 3. Note that the automotive headlamp illustrated is to be mounted on the left side of an automobile for right traffic. An automotive headlamp to be mounted on an automobile for left traffic is the reverse of this illustrated automotive headlamp in the horizontal arrangement of a reflecting surface 40, a high-beam filament 52, and the like. Moreover, an automotive headlamp to be mounted on the right side of an automobile, while identical to this illustrated automotive headlamp in the arrangement of the reflecting surface 40, the high-beam filament 52, and the like, replaces its lamp housing 1, lens 2, and reflector 4 with those generally symmetrical in shape.
This automotive headlamp has a lamp chamber 3 defined by the lamp housing 1 and the lens (outer lens) 2. In this lamp chamber 3, the reflector 4 separately formed from the lamp housing 1 is arranged to be rotatable in vertical and horizontal directions, by a pivot mechanism (not shown), an optical axis adjustment mechanism (not shown), and the like. This reflector 4 has a reflecting surface 40 constituted by a complex reflecting surface. This reflecting surface 40, i.e. the complex reflecting surface, comprises reflecting surface segments (not shown) sectioned in a plurality of pieces all around, and is referred to as so-called free-form curved surface. This complex reflecting surface, as described in Japanese Patent Laid-Open Publication No. Hei 9-306220. for example, includes that divided into a large number of blocks, that divided into a small number of blocks, and that having a plurality of blocks continuously connected with one another (the connecting lines therebetween not being visible).
In the strict sense, this complex reflecting surface has more than one single focus. The plurality of paraboloids of revolution constituting the complex reflecting surface, however, differ in focal length from each other but merely slightly, and practically share the same focus. Thus, the focus will be referred to as focus F in the present specification document, while the focus F shown in the drawings is a pseudo focus in the strict sense. Similarly, while the optical axis Z-Z (also referred to as reference axis Z-Z) shown in the drawings is a pseudo optical axis in the strict sense, it will be referred to as optical axis in the present specification document.
To the above-described reflector 4 is detachably attached a light source bulb 5. This light source bulb 5 is a light source bulb with no shading hood, in which a low-beam (dipped-beam) filament 51 and a high-beam (main-beam) filament 52 are arranged in a glass envelope 50, and this glass envelope is provided with, e.g., coating 54 of black paint (for intercepting direct lights from the low-beam filament 51 and high-beam filament 52 to the lens 2) at an extremity thereof.
The low-beam filament 51 mentioned above forms a generally cylindrical shape of coil structure, and is generally parallel to the optical axis Z-Z. This filament 51 is positioned forward of the focus F. The high-beam filament 52 also forms a generally cylindrical shape of coil structure, and is generally parallel to the optical axis Z-Z. This filament 52 is positioned in the vicinity of the focus F and obliquely below the low-beam filament 51 (at the lower rightward as shown in FIG. 11A, for the right-traffic; at the lower leftward as shown in FIG. 6C, for the left-traffic). The central axis of the low-beam filament 51 described above generally coincides with the aforementioned optical axis Z-Z (reference axis Z-Z), and lies below the central axis of the aforementioned glass envelope 50, i.e., below the envelope axis Zxe2x80x2-Zxe2x80x2. The reason why the central axis Z-Z of this low-beam filament 51 is positioned below the envelope axis Zxe2x80x2-Zxe2x80x2 is to obtain a stable light-shade boundary line 71 (so-called cut line) in the low-beam distribution pattern shown in FIG. 4 to be described later. That is, as previously known, the central axis Z-Z of the low-beam filament 51 is shifted to downward of the envelope axis Zxe2x80x2-Zxe2x80x2 to prevent the converged image (virtual image) of the reflected light in the inner peripheral portion of the glass envelope 50 from appearing above the light-shade boundary line 71 of the low beam distribution pattern LP.
In the drawings, reference numeral 6 designates a shade. This shade 6 is fixed to the aforesaid reflectors 4 and covers the front of the aforesaid light source bulb 5, so as to intercept the direct lights from the low-beam filament 51 and the high-beam filament 52 to the invalid portions 42 (portions with no direct involvement to the light distribution of the headlamp) of the reflector 4 and to the lens 2. In addition, reference numeral 60 designates a rubber cap. This rubber cap 60 is watertightly and detachably attached to between the base of the light source bulb 5 and the rear opening portion of the lamp housing 1 via an attaching cap 61, thereby maintaining the interior of the lamp chamber 3 watertight.
Now, when in the automotive headlamp described above the low-beam filament 51 is lit, lights from this low-beam filament 51 are reflected over the entire surface of the reflecting surface 40 of the reflector 4, and the reflected lights are irradiated out through the lens 2 with the prescribed low beam distribution pattern LP shown in FIG. 4. When in contrast the high-beam filament 52 is lit, lights from this high-beam filament 52 are reflected over the entire surface of the reflecting surface 40, and the reflected lights are irradiated out through the lens 2 with a prescribed high beam distribution pattern HP shown in FIG. 5.
In this way, the prescribed low beam distribution pattern LP and the prescribed high beam distribution pattern HP each is formed by the entire-surface reflection light distribution control of the reflecting surface 40 of the reflector 4.
The prescribed low beam distribution pattern LP and prescribed high beam distribution pattern HP mentioned above designate those light distribution patterns conformable to light distribution standards such as ECE Reg. the European light distribution standards, the ones based on the same (e.g., Japanese type approval standard and the like), and FMVSS the North America light distribution standards.
The low beam distribution pattern LP described above is standardized in light distribution so as to limit the occurrence of glare. This results in the aforementioned low beam distribution pattern LP with the light-shade boundary line 71, as shown in FIG. 4, taking account of a car 7 on the opposite lane and a pedestrian 70 on the right shoulder of the road. More specifically, this light-shade boundary line 71 comprises a horizontal line portion 72, a gentle tilt line portion 73, and a tilt line portion 74. The horizontal line portion 72 extends from the left end to the approximate center, lying somewhat below the horizontal line HL-HR so as not to cause glare to the car 7 on the opposite lane. The gentle tilt line portion 73 tilts up rightward from the horizontal line portion 72 at the approximate center with a gentle angle, e.g. an angle of 15xc2x0, so as to observe the pedestrian 70 on the right shoulder without causing glare to the pedestrian 70. The tilt line portion 74 tilts down rightward from the gentle tile line portion 73 to return to the horizontal line portion 72 again. This low beam distribution pattern LP has no standard on the maximum value of light intensity. In contrast, the high beam distribution pattern HP mentioned above is standardized in light distribution on the maximum value of light-intensity and the maximum light intensity zone. This results in the above-mentioned high beam distribution pattern HP having a hot zone HZ (the maximum light intensity zone including the maximum light intensity point) at the center, as shown in FIG. 5. Here, in the European light distribution standards ECE Reg., the maximum value of light intensity is 48-240 lx (1 1x=625 cd; measurement on a 25-m-away screen), and the value of light intensity at the intersection between the horizontal line HL-HR and the vertical line VU-VD is equal to or greater than 80% (certified) the maximum value of light intensity.
What is important in the automotive headlamp described above is that a favorable low beam distribution pattern LP can be obtained without causing the glare problem, as well as that a favorable high beam distribution pattern can be obtained.
Here, the light source bulb 5 described above is divided into a left-traffic light source bulb 5L for use in an automotive headlamp for left traffic or a right-traffic light source bulb 5R for use in an automotive headlamp for right traffic, both for dedicated use. More specifically, the left-traffic light source bulb 5L has a high-beam filament 52 positioned at the lower leftward of its low-beam filament 51, as shown in FIGS. 6C and 15A. Meanwhile, the right-traffic light source bulb 5R has a high-beam filament 52 positioned at the lower rightward of its low-beam filament 51, as shown in FIGS. 11A and 12A. Thus, the high-beam filaments 52 in the left-traffic light source bulb 5L and the right-traffic light source bulb 5R are arranged in symmetric positions to each other with respect to the central axis Z-Z of the low-beam filament 51.
On this account, the light source bulb 5 described above is rotated to the right or left about the central axis Z-Z of the low-beam filament 51 so that the light source bulb 5 can cope with both the left-traffic light source bulb 5L and the right-traffic light source bulb 5R in one.
However, depending on conditions in constituting the light source bulb 5, the above-described rotation can produce a change in light distribution which might be an obstacle to the function of the low-beam filament 51, i.e., a glare problem.
Hereinafter, the aforementioned glare problem will be described in conjunction with the case of resulting from lead wires and support wires of the light source bulb 5 and the case of resulting from the glass envelope of the light source bulb 5, with reference to FIGS. 6A-11C and FIGS. 12A-15D, respectively.
First, description will be given of the glare problem resulting from lead wires and support wires of the light source bulb 5.
In a left-traffic light source bulb 5L, lead wires LW1, LW2, LW3, and LW4, and support wires SW1, SW2, and SW3 are arranged as shown in the neutral state of FIGS. 6B, 7, and 8. More specifically, a first lead wire LW1 extended from the front end 51A (the corner between the front end 51A and upper end 51U) of the low-beam filament 51 is supported on the front end portion of a first support wire SW1. A second lead wire LW2 extended from the rear end 51B (the corner between the rear end 51B and upper end 51U) of the low-beam filament 51 is supported on the upper part of the vertical bent part of a second support wire SW2. A third lead wire LW3 extended from the rear end 52B (the corner between the rear end 52B and upper end 52U) of the high-beam filament 52 is supported on the lower part of the vertical bent part of the aforesaid second support wire SW2. A fourth lead wire LW4 extended from the front end 52A (the corner between the front end 52A and lower end 52D) of the high-beam filament 52 is supported on the front end portion of a third support wire SW3. Each of the aforesaid support wires SW1, SW2, and SW3 is supported on a bridge 57 made of glass. The aforesaid first lead wire LW1, second lead wire LW2, third lead wire LW3, first support wire SW1, and second support wire SW2 are positioned on the vertical line VU-VD connecting the low-beam filament 51 to the high-beam filament 52. The aforesaid fourth lead wire LW4 and third support wire SW3 lie at approximately the same level as that of the high-beam filament 52. This third support wire SW3 is extended from the bridge 57 to the front partway, where the wire is once bent leftward to avoid the high-beam filament 52 before it is bent again and extended to the front.
This left-traffic light source bulb 5L in its neutral state shown in FIGS. 6B, 7, and 8 is then rotated to the right or left about the central axis Z-Z of the low-beam filament 51, and built into an automotive headlamp for left traffic in the state shown in FIG. 6C for use. Lighting the low-beam filament 51 of this left-traffic light source bulb 5L offers a prescribed low beam distribution pattern (light distribution pattern horizontally inverted from the low beam distribution pattern LP shown in FIG. 4). Lighting the high-beam filament 52 offers a prescribed high beam distribution pattern (light distribution pattern horizontally inverted from the high beam distribution pattern HP shown in FIG. 5). When the low-beam filament 51 is lit as mentioned above, the radiation of the low-beam filament 51 illuminates each wire LW1, LW2, LW3, LW4, and each support wire SW1, SW2, SW3 to shine (the closer to the low-beam filament 51 and the larger the exposed area is, the higher the intensity is).
Here, in the cases where the left-traffic light source bulb 5L in its neutral state is rotated to the right or left about the central axis Z-Z of the low-beam filament 51 and built into a right-traffic automotive headlamp in the state shown in FIG. 6A for use, a glare problem arises as described below.
That is, when the left-traffic light source bulb 5L is incorporated with a right-traffic automotive headlamp for use, the fourth lead wire LW4 and the third support wire SW3 are positioned below the lower end 51D of the lower-beam filament 51, as shown in FIG. 6A. On this account, as shown in FIG. 9, the lower end 51D of the low-beam filament 51 appears above the light-shade boundary line 71 (the horizontal line portion 72, the gentle tilt line portion 73), and the low-beam filament 51, the first lead wire LW1, second lead wire LW2, and first support wire SW1 (also including the high-beam filament 52, third lead wire LW3, and second support wire SW2, even though omitted of illustration in FIG. 9) appear below the light-shade boundary line 71. Meanwhile, the aforesaid fourth lead wire LW4 and third support wire SW3 positioned below the lower end 51D of the low-beam filament 51 appear above the light-shade boundary line 71 (the horizontal line portion 72, the gentle tilt line portion 73). Incidentally, in FIG. 9, the images of the low-beam filament 51, the high-beam filament 52, each lead wire LW1, LW2, LW3, LW4, and each support wire SW1, SW2, SW3 are diffused to the right and left, or to the upper right and lower left, as shown by the arrows.
As a result, the fourth lead wire LW4 and third support wire SW3 described above make virtual image glare. This causes, as shown in FIG. 10, the virtual image glare VIG to appear on the point P (B50L; a point shown by the double circle in FIG. 10) and zone Z (zone III; a part shown by the oblique lines in FIG. 10, exceeding the limit) where glare is severely restricted by the European light distribution standards ECE Reg.
The foregoing constitutes the description on the production of the glare problem in the case where a left-traffic light source bulb 5L is built into a right-traffic automotive headlamp for use. Hereinafter, referring to FIG. 11, description will be made on the glare problem in the case where a right-traffic light source bulb 5R is incorporated with a left-traffic automotive headlamp for use.
As shown in its neutral state of FIG. 11B, this right-traffic light source bulb 5R has a fourth lead wire LW4 and a third support wire SW3 positioned on the right of its high-beam filament 52, at approximately the same level as that of the high-beam filament 52. On this account, no glare problem arises when the bulb in its neutral state shown in FIG. 11B is rotated to the right or left about the central axis Z-Z of the low-beam filament 51 and incorporated with a right-traffic automotive headlamp for use in the state shown in FIG. 11A. In contrast, when the bulb in its neutral state shown in FIG. 11B is rotated to the right or left about the central axis Z-Z of the low-beam filament 51 and built into a left-traffic automotive headlamp for use in the state shown in FIG. 11C, the third support wire SW3 and the fourth lead wire LW4 are situated below the lower end 51D of the low-beam filament 51, which gives rise to a problem of the virtual image glare as in the above-described case where the left-traffic light source bulb 5L is used in a right-traffic headlamp.
Thus, in conventional light source bulbs 5, a single (identical) light source bulb 5 cannot be used both as a left-traffic light source bulb 5L and a right-traffic light source bulb 5R. In other words, a left-traffic automotive headlamp uses the left-traffic light source bulb 5L shown in FIGS. 6B, 7, and 8, in the state of FIG. 6C, and a right-traffic automotive headlamp uses the right-traffic light source bulb 5R shown in FIG. 11B, in the state of FIG. 11A.
Moreover, when in the conventional light source bulbs 5L and, 5R described above the lower end SW2xe2x80x2 of the vertical bent part on the front end portion of the second support wire SW2 is provided below a product L8 drawn from the lower end 51D of the low-beam filament 51 as shown in FIGS. 6A-6C, 8, and 11A-C, the lower end SW2xe2x80x2 of the second support wire SW2 can sometimes be situated below the lower end 51D to produce the problem of the virtual image glare.
Next, description will be made on the glare problem resulting from the glass envelope of the light source bulb 5.
The glass envelope 50 of a light source bulb 5r to be used for a right-traffic automotive headlamp has a hollow cylindrical shape, as shown in FIGS. 12A-12D. The rear end part 53 of this glass envelope 50 is sealed at portions on both the right and left sides with respect to the vertical line VU-VD. As shown in FIG. 12A, this results in the central portion 53C of the rear-end sealed part 53 being squeezed into a generally rectangular, planar shape elongated along the vertical line VU-VD as seen from the front. Besides, as shown in FIG. 12C, the portions 53L and 53R on the both right and left sides of this rear-end sealed part 53 are deformed to curve as seen in plan (from the top).
On this account, when the right-traffic light source bulb 5R shown in. FIGS. 12A, C, and D is rotated to the right or left about the central axis Z-Z of the low-beam filament 51 for use as the left-traffic light source bulb shown in FIG. 12B, the curve-deformed portions 53L; and 53R on the left and right are situated up and down. Under the up and down situations of the left and right curve-deformed portions 53L and 53R, the light from the low-beam filament 51 through the middle envelope part (having al flat-shaped cross-section), as shown in FIG. 13, keeps proceeding straight as shown by the arrowed broken line, causing no problem to the low beam distribution pattern LP; in the meantime, the light passing through the left curve-deformed portion 53L situated up changes its optical path as shown by the arrowed full line, which may produce glare on the low beam distribution pattern LP and create a light distribution problem, possibly causing a trouble in terms of the light distribution standards mentioned above.
In order to solve the problem mentioned above, it is therefore contemplated to cover the curve-deformed portions 53L and 53R with a ring-shaped cap 58. The fitting of this cap 58, however, causes another problem described below. That is, lights L10, L20, L30, and L40 from the low-beam filament 51 and high-beam filament 52 are intercepted by the cap 58 with great losses D1 and D2 in the quantity of distributed lights. Incidentally, in FIG. 14, L10 designates the light extending from the corner 51BU formed between the rear end and upper end of the low-beam filament 51 through the corner of the cap 58; L20 the light extending from the corner 51BD formed between the rear end and lower end of the low-beam filament 51 through the corner of the cap 58; L30 the light extending from the corner 52BU formed between the rear end and upper end of the high-beam filament 52 through the corner of the cap 58; L40 the light extending from the corner 52BD formed between the rear end and lower end of the high-beam filament 52 through the corner of the cap 58; D1 the loss area (invalid portion) of the quantity of distributed low beam; and D2 the loss area (invalid portion) of the quantity of distributed high beam. The fitting of the cap 58 also increases the number of component parts, the number of assembling processes and the like, which is undesirable in terms of costs.
The foregoing constitutes the description on the production of the glare problem in the case where a right-traffic light source bulb 5R is built into a left-traffic automotive headlamp for use. Similarly, when the left-traffic light source bulb 5L shown in FIGS. 15A, C, and D is rotated to the right or left about the central axis Z-Z of the low-beam filament 51 for use as a right-traffic light source bulb shown in FIG. 15B, the right and left curve-deformed portions 53R and 53L are also situated up and down to cause the glare problem as described above.
Thus, in conventional light source bulbs 5, a single (identical) light source bulb 5 cannot be used both as a left-traffic light source bulb 5L and a right-traffic light source bulb 5R. In other words, a left-traffic automotive headlamp uses the left-traffic light source bulb 5L in the state of FIG. 12A, and a right-traffic automotive headlamp uses the right-traffic light source bulb 5R in the state of FIG. 15A.
It is an object of the present-invention to provide a light source bulb in an automotive headlamp, which can be used both as a left-traffic light source bulb and a right-traffic light source bulb.
To achieve the foregoing object, a first invention is characterized in that: in the case where the light source bulb is used as a right-traffic light source bulb and as left-traffic light source bulb, at least one of the lead wires and the support wires situated below the low-beam filament lies in the shading coverage of the high-beam filament when the low-beam filament is lit.
Consequently, due to the configuration described above, the light source bulb of the first invention, even in either use as a right-traffic light source bulb or a left-traffic light source bulb, puts at least one of the lead wires and support wires situated below the low-beam filament into the shading coverage of the high-beam filament in the lighting of the low-beam filament. Therefore, when the low-beam filament is lit, the aforementioned at least one of the lead wires and support wires is prevented from exposure to the irradiating lights from the low-beam filament by the effect of the shading function of the high-beam filament, getting rid of virtual image glare. Moreover, all of the aforementioned lead wires and support wires situated below the low-beam filament can be put into the aforementioned shading coverage of the high-beam filament to surely solve the glare problem.
Besides, in order to achieve the foregoing object, a second invention is characterized in that the boundary between the middle envelope part and the rear-end sealed part of the glass envelope is positioned behind a line connecting the corner formed between the rear end and upper end of the high-beam filament to a corner formed between the reflecting surface of the reflector and the inner periphery of the insertion through-hole.
This results in that: due to the configuration described above, the light source bulb of the second invention, in either use as a right-traffic light source bulb or a left-traffic light source bulb, has the lights from the low-beam filament and high-beam filament reaching the reflecting surface of the reflector without passing through the rear-end sealed part of the glass envelope, even when the right and left curve-deformed portions are situated up and down. This eliminates the optical-path changes in the rear-end sealed part, the production of glare light, and the problem with light distribution. In addition, the lights from the low-beam filament and the high-beam filament reach the entire reflecting surface of the reflector, thereby eliminating the loss in quantity of the low beam and the high beam.
Furthermore, in order to achieve the foregoing object, a third invention is characterized in that the boundary between the middle envelope part and the rear-end sealed part of the glass envelope is positioned behind a line connecting the corner formed between the rear end and upper end of the low-beam filament in its initial state to a corner formed between the reflecting surface of the reflector and the inner periphery of the insertion through hole.
This results in that: due to the configuration described above, the light source bulb of the third invention, in either use as a right-traffic light source bulb or a left-traffic light source bulb, has the lights from the low-beam filament reaching the reflecting surface of the reflector without passing through the rear-end sealed part of the glass envelope, even when the right and left curve-deformed portions are situated up and down. This eliminates the optical-path changes in the rear-end sealed part, the production of glare light, and the problem with light distribution. In addition, the lights from the low-beam filament reach the entire reflecting surface of the reflector, thereby eliminating the loss in quantity of the low beam.
Thus, the light source bulbs of the present invention can be used both as a left-traffic light source bulb and a right-traffic light source bulb in one.
The nature, principle and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.